It is customary to provide speed reducing mechanisms with hollow power takeoff shafts or sleeves so that they may interchangeably receive therein the shafts of mechanisms to be driven thereby. Since clearance is required between the driven shaft and the power takeoff sleeve in order to provide for the convenient detachable mounting of the speed reducer on the driven shaft some means for establishing and maintaining the precise concentricity of the power takeoff sleeve and driven shaft therein is required in order to prevent any wobble.
In some prior arrangements for establishing concentricity between these members exteriorly tapered and longitudinally split bushings were inserted into the similarly internally tapered ends of the power takeoff sleeve. These bushings normally loosely fitted the shaft to be driven and were drawn into the tapered ends of the sleeve by screw threaded means so as to contract and grip the driven shaft. This resulted in substantial frictional engagement of the bushings with both the driven shaft and power takeoff sleeve. In some prior arrangements of this kind the driving connection between the power takeoff sleeve and driven shaft depended upon this friction between the contracted bore of the bushings and driven shaft and between the exteriorly tapered surfaces of the bushings and interiorly tapered surfaces at the ends of the power takeoff sleeve. In other arrangements of this kind feather keys were employed keying the sleeve to the driven shaft in addition to the frictional engagement of the split bushings with the sleeve and driven shaft.
Because of the considerable torque which is frequently transmitted between the sleeve and driven shaft it has been found desirable to avoid transmitting any torque through the frictionally engaged surfaces which function to establish precise concentricity lest this concentricity be disturbed thereby and to transmit all torque positively and completely independently of these frictionally engaged surfaces through suitable keys. Moreover, it was found desirable to reduce the required contraction of the tapered split bushings functioning to effect concentricity to a minimum so as to minimize their deviation from a perfect circle when contracted. This may be accomplished by sizing the inside diameters of the bushings close to yet accommodating established industry standards for diametral tolerances of cold rolled shafting so as to permit the convenient slidable mounting of the bushings on the driven shaft. Accordingly we have provided improved means for the convenient detachable and precise concentric mounting and drive coupling of a speed reducer having a power takeoff sleeve on a shaft to be driven thereby which incorporates the above desirable features.